Non-volatile semiconductor memory apparatus

ABSTRACT

The invention achieves a high speed access when shifting to an active mode from a standby mode, in particular immediately after shifting to a read, and reduces the current consumption at the time of standby. A strong charge pump generates 5.0V and a power supply voltage of 8.0V. The power supply voltage is supplied to constant voltage circuits. The constant voltage circuits generate voltages VPBL, VPYS, VPCGL, VPCGL, VPCGH and VPCGH, respectively, according to the respective read, program and erase operation modes. The constant voltage circuit that operates in active modes consumes a large amount of current when it supplies the voltage VPCGH. In contrast, the constant voltage circuit operates with a low current consumption and generates the voltage VPCGH in the standby mode. With the voltage VPCGH that is generated by the constant voltage circuit in the standby mode, a high speed access is possible when shifting from the standby mode to the active mode, and in particular, immediately after shifting to a read mode. Also, the current consumption in the standby mode can be substantially reduced.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates to non-volatile semiconductor memoryapparatuses, and more particularly to non-volatile semiconductor memoryapparatuses equipped with charge pump devices that step up power supplyvoltage.

2. Description of Related Art

Semiconductor memory apparatuses may be classified into a variety ofdifferent types depending on their functions. Such semiconductor memoryapparatuses include a memory cell array that is formed of memory cellsarranged in a matrix. In general, an address in a row direction and acolumn direction in the memory cell array is designated in performing areading, programming or erasing operation for each of the memory cells.

By controlling voltages applied to a signal line in the row directionand a signal line in the column direction that are connected to each ofthe memory cells, a specified memory cell can be accessed, such that aspecified operation among reading, programming and erasing operationsthereof can be performed. In other words, in order to select a specifiedmemory cell, a voltage different from other voltages to be applied toother memory cells may be generated from the power supply voltage andapplied.

Recently, MONOS (Metal-Oxide-Nitride-Oxide-Semiconductor or -substrate)type devices have been developed as non-volatile semiconductor devicesthat are electrically erasable and have non-volatility. A MONOS typenon-volatile semiconductor memory apparatus has memory cells that eachhave two memory elements, as described in detail in a publication (Y.Hayashi, et al., 2000 Symposium on VLSI Technology Digest of TechnicalPapers p. 122-p. 123).

As described in this publication, to access each of the memory elementsof the MONOS type non-volatile semiconductor memory apparatus via signallines (control lines) that are provided according to the number of thememory cells, not only two kinds of voltage values, but a plurality ofkinds of voltage values need to be set for each of the signal lines(control lines).

In this case, devices that each have a pair of a charge pump circuitthat operates with the power supply voltage and a regulator may beprepared in the number of kinds of voltages required for each of theoperations of the memory.

SUMMARY OF THE INVENTION

The response of the charge pump is slow due to restrictions of its clockfrequencies and the like. Accordingly, when the operation of the chargepump circuit is stopped in a standby mode, it takes a long time, aftershifting to an active mode, in particular when shifting to a read thatrequires a high voltage, to reach an accessible state.

In this respect, the charge pump may be operated even during a standbymode, and a high voltage is maintained by the charge pump, and aregulator may be used to generate required operation voltages.

However, the amount of current that circulates in the charge pump and aregulator that generates operation voltages to read in particular isextremely large. Therefore, it is a problem that the current consumptionin the standby mode is high.

The present invention addresses the problems described above, andprovides a non-volatile semiconductor memory apparatus that cansubstantially reduce the current consumption in a standby mode by usinga regulator for standby with a low current consumption.

A non-volatile semiconductor memory apparatus in accordance with thepresent invention includes: a charge pump device that steps up andoutputs a power supply voltage; an operation voltage setting device thatsets operation voltages to execute plural modes for a specifiednon-volatile memory element within a memory array formed of theplurality of non-volatile memory elements; a constant voltage device foractivation that is provided with voltages output from the charge pumpdevice to generate the operation voltages in an active state; and aconstant voltage device for standby that is provided with a voltageoutput from the charge pump device to generate a voltage based on theoperation voltage with a lower current consumption than voltagesgenerated by the constant voltage device for activation.

With this structure, the charge pump device steps up the power supplyvoltage and supplies the same to the constant voltage devices foractivation and standby. The constant voltage device for activation, atthe time of activation, generates operation voltages from the output ofthe charge pump device and supplies the same to the operation voltagesetting device. The operation voltage setting device uses voltagesgenerated by the constant voltage device for activation to set operationvoltages to execute various modes, such as, for example, a read mode,program mode and erase mode. In contrast, at the time of standby, theconstant voltage device for standby generates operation voltages fromthe output of the charge pump device. The constant voltage device forstandby causes a low current consumption, such that the currentconsumption amount at the time of standby can be markedly reduced. Also,voltages based on the operation voltages are generated even at the timeof standby, such that a high speed access becomes possible even in ashift from a standby mode to an active mode.

The operation voltage generated by the constant voltage device forstandby is a voltage higher than the power supply voltage.

With this structure, even when the power supply voltage is stepped up togenerate operation voltages, the current consumption at the time ofstandby can be reduced, and a high speed access when shifting to anactive mode can be achieved.

The constant voltage device for standby generates an operation voltagefor a read mode for the non-volatile memory element.

With this structure, at the time of reading, high operation voltages andhigh speed response are required. Since the constant voltage device forstandby generates voltages based on the operation voltages to providereading, a high speed access is made possible even when shifting to anactive mode.

The charge pump device steps up the power supply voltage to generate aplurality of voltages.

With this structure, the range of voltage values that can be generatedby one or a plurality of constant voltage devices can be broadened.

The constant voltage device is capable of generating constant voltagesof different voltage values depending on read, program or erase mode forthe non-volatile memory element.

With this structure, the constant voltage device can obtain constantvoltages according to an operation mode, i.e., a read mode, a programmode or an erase mode. Therefore, when a plurality of operation voltagesare required for each of the modes, each mode can be executed.

The non-volatile memory element is a memory element that forms a twinmemory cell controlled by one word gate and first and second controlgates.

With this structure, for example, a reading operation, a programmingoperation or an erasing operation can be performed for the memory arraywith twin memory cells.

The operation voltage setting device is characterized in that it setsvoltage values provided from the constant voltage device independentlyfor the first and second control gates, and an impurity layer to accesstrapped charge of the non-volatile memory element.

With this structure, the operation voltage setting device sets operationvoltages required for a word gate that selects a twin memory cell, setsoperation voltages required for the first and second control gates toselect a non-volatile memory element within the selected twin memorycell, and sets required operation voltages for an impurity layer toaccess trapped charge of the selected non-volatile memory element. As aresult, for example, a reading operation, a programming operation or anerasing operation can be performed for a specified non-volatile memoryelement in a specified twin memory cell.

The operation voltage setting device includes: a word line connected toa word gate of the twin memory cell in the same row; a control gate linethat is commonly connected to the mutually adjacent first and secondcontrol gates in the same column of the twin memory cells arrangedadjacent to each other in a row direction; and a bit line that iscommonly connected to impurity layers to access trapped charge arrangedin the same column of the mutually adjacent non-volatile memory elementsof the twin memory cells arranged adjacent to each other in the rowdirection. Voltages provided from the constant voltage device are setindependently for the control gate line and the bit line.

With this structure, the operation voltage setting device selects withthe word line twin memory cells in the same row, commonly selects withthe control gate line mutually adjacent first and second control gatesin the same column of the twin memory cells arranged adjacent to eachother in the row direction, and commonly selects with the bit lineimpurity layers in the same column to access trapped charge of themutually adjacent non-volatile memory elements of the twin memory cellsarranged adjacent to each other in the row direction. As a result, evenwhen a memory array is formed of numerous non-volatile memory elements,sections at which operation voltages are to be set can be reduced.

Also, a non-volatile semiconductor memory apparatus in accordance withthe present invention includes: a charge pump device that steps up andoutputs a power supply voltage; an operation voltage setting device thatsets an operation voltage to execute each of reading, programming anderasing operations for a specified non-volatile memory element within amemory array composed of a plurality of twin memory cells each havingtwo non-volatile memory elements controlled by one word gate, and firstand second control gates; a constant voltage device for activation thatis provided with voltages output from the charge pump device to generatethe operation voltages in an active mode; and a constant voltage devicefor standby that is provided with a voltage output from the charge pumpdevice to generate in an active mode a voltage based on the operationvoltage to be supplied to the first and second control gates in a readmode with a lower current consumption than voltages generated by theconstant voltage device for activation.

With this structure, the operation voltage setting device sets operationvoltages required for the first and second control gates to therebyselect a non-volatile memory element within a twin memory cell. Moreparticularly, at the time of reading, the change cycle of operationvoltages supplied to the first and second control gates is shortcompared to the other operation modes. However, at the time of standby,the charge pump device generates operation voltages to be supplied tothe first and second control gates with a lower current consumption thanthose generated by the constant voltage device for activation, andtherefore a high speed access is possible even immediately aftershifting to a read.

The non-volatile memory element has an ONO film formed of an oxide film(O), a nitride film (N) and an oxide film (O) as a charge trap site.

With this structure, operation voltages of an apparatus using a MONOStype non-volatile memory can be set.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of a non-volatile semiconductor memory apparatusin accordance with a first embodiment of the present invention;

FIG. 2 is a schematic that shows a cross-section of a structure of twinmemory cells;

FIGS. 3(A)-(E) are schematics that show a non-volatile semiconductormemory apparatus;

FIG. 4 is a schematic that shows a circuit diagram of a small block;

FIG. 5 is a schematic for describing numerous small blocks and theirwirings of one sector;

FIG. 6 is a schematic indicating the relation between small blocks andlocal drivers in two adjacent sectors;

FIG. 7 is a schematic that shows a circuit diagram indicating therelation between small blocks and control gate drivers;

FIG. 8 is a schematic indicating a selected block, a non-selectedopposing block opposing the selected block, and other non-selectedblocks;

FIG. 9 is a schematic that shows an equivalent circuit of a memory cell;

FIG. 10 is schematic for describing a data read operation in anon-volatile semiconductor memory apparatus;

FIG. 11 is a schematic for describing voltages set within a selectedblock at the time of data reading;

FIG. 12 is a graph that shows characteristic curves indicating therelation between control gate voltages VCG and source-drain currents Idsin a memory cell;

FIG. 13 is a schematic for describing voltages set within a non-selectedopposing block at the time of data reading;

FIG. 14 is a schematic for describing voltages set within non-selectedblocks other than the opposing block at the time of data reading;

FIG. 15 is a schematic for describing a data write (program) operationin a non-volatile semiconductor memory apparatus;

FIG. 16 is a schematic for describing voltages set within a selectedblock at the time of data programming;

FIG. 17 is a schematic that shows a circuit diagram of a Y pass circuitthat is connected to a bit line;

FIG. 18 is a schematic for describing voltages set within a non-selectedopposing block at the time of data programming;

FIG. 19 is a schematic for describing voltages set within non-selectedblocks other than the opposing block at the time of data programming;

FIG. 20 is a schematic for describing voltages set within a selectedblock at the time of data programming for a memory element on theselected side, which is different from FIG. 16;

FIG. 21 is a schematic for describing a data erase operation in anon-volatile semiconductor memory apparatus;

FIG. 22 is a schematic for describing voltages set within a selectedblock at the time of data erasing;

FIG. 23 is a schematic for describing voltages set within a non-selectedopposing block at the time of data erasing;

FIG. 24 is a schematic for describing voltages set within non-selectedblocks other than the opposing block at the time of data erasing;

FIG. 25 is a schematic that shows a block diagram of a concretestructure of a voltage generation circuit shown in FIG. 1;

FIG. 26 is a schematic that shows a circuit diagram of a concretestructure of a charge pump 22 shown in FIG. 25;

FIG. 27 is a schematic that shows a circuit diagram of a concretestructure of constant voltage circuits 13-18 shown in FIG. 25.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Embodiments of the present invention are described below in detail withreference to the accompanying drawings. FIG. 1 is a schematic of anon-volatile semiconductor memory apparatus in accordance with a firstembodiment of the present invention.

The present embodiment enables a voltage generation circuit having onecharge pump to supply multiple kinds of voltages to an array block thatis formed with twin memory cells.

Also, in accordance with the present embodiment, in the read mode, amargin of the charge pump output against a required operation voltage ismade to be greater than in other operation modes, such that the outputof the charge pump is always maintained at a voltage greater than therequired operation voltage.

Also, the present embodiment uses regulators (constant voltage circuit)with low current consumption, and changes the regulators to be used in astandby mode and in an active mode so that the current consumption inthe standby mode can be reduced.

First, referring to FIG. 2, a structure and operation of twin memorycells forming an array block are described. FIG. 2 schematically shows across-section of a structure of twin memory cells.

As shown in FIG. 2, a plurality of twin memory cells 100 ( . . . , 100[i], 100 [i+1], . . . ) are arranged on a P-type well 102 in B direction(hereafter “row direction” or “word line direction”). As describedbelow, the twin memory cells 100 are also arranged in plurality in acolumn direction (a direction that is perpendicular to the paper surfaceof FIG. 2) (hereafter “bit line direction”), so as to be arranged in amatrix.

Each of the twin memory cells 100 is formed from a word gate 104 that isformed over the P-type well 102 through a gate dielectric layer, firstand second control gates 106A and 106B, and first and second memoryelements (MONOS memory elements) 108A and 108B.

Each of the first and second memory elements 108A and 108B includes anONO film 109 that is formed of an oxide film (O), a nitride film (N) andan oxide film (O) stacked in layers, and is capable of trapping chargein the ONO film 109. First and second control gates 106A and 106B areformed on the ONO films 109 of the first and second memory elements,respectively. Operating conditions of the first and second memoryelements 108A and 108B are controlled by the first and second controlgates 106A and 106B which are formed from polysilicon that correspondsto M (metal) of MONOS. It is noted that the first and second controlgates 106A and 106B may be formed from conductive material such assuicide.

A word gate 104, which is formed of material including, for example,polysilicon, is formed electrically insulated from and between the firstand second memory elements 108A and 108B. Voltages applied to the wordgate 104 determine whether or not the first and second memory elements108A and 108B of each of the twin memory cells 100 are selected.

In this manner, each of the twin memory cells 100 includes first andsecond MONOS memory elements 108A and 108B equipped with split gates(first and second control gates 106A and 106B), and one word gate 104 isshared by the first and second MONS memory elements 108A and 108B.

The first and second MONOS memory elements 108A and 108B independentlyfunction as charge trap sites. The word gates 104, which controltrapping of charge, are arranged in the row direction at intervals asshown in FIG. 2, and commonly connected to one word line WL which isformed from polycide or the like. By supplying a specified signal to theword line WL, at least one of the first and second memory elements ineach of the twin memory cells 100 in the same row can be selected.

Each of the control gates 106A and 106B extends along the columndirection, and is shared by a plurality of twin memory cells 100 thatare arranged in the same column, and functions as a control gate line.The mutually adjacent control gates 106A and 106B of the memory cells100 that are arranged adjacent to one another in the row direction arecommonly connected to a sub-control gate line SCG ( . . . , SCG [i], SCG[i+1], . . . ). The sub-control gate line SCG may be formed of a metallayer that is formed in a layer above the control gates 106A and 106Band the word line WL.

By applying a voltage to each of the sub-control gate lines SCGindependently from one another, the two memory elements 108A and 108B ineach of the memory cells 100 can be controlled independently of eachother.

An impurity layer 110 ( . . . , 110 [i], 110 [i+1], . . . ) is formed inthe P-type well 102 between the mutually adjacent memory elements 108Aand 108B of the memory cells 100 that are arranged adjacent to oneanother in the row direction. The impurity layers 110 are, for example,n-type impurity layers formed in the P-type well 102, extend in thecolumn direction, are shared by a plurality of twin memory cells 100that are arranged in the same column, and function as bit lines BL ( . .. , BL [i], BL [i+1], . . . ).

By application of voltages and current detection with respect to the bitlines BL, reading and programming of charge (data) can be performed forone of the memory elements in each of the memory cells 100 which isselected by the word line WL and the sub-control gate line SCG.

(Overall Structure Of Non-volatile semiconductor memory apparatus)

An overall structure of a non-volatile semiconductor memory apparatusthat is structured using the above-described twin memory cells 100 isdescribed with reference to FIGS. 3(A) through 3(E). FIGS. 3(A)-3(E) areschematics of more concrete compositions of the array block shown inFIG. 1.

FIG. 3(A) is a schematic of a non-volatile semiconductor memoryapparatus in one chip, and includes a memory cell array region 200 and aglobal word line decoder 201. The memory cell array region 200 includes,for example, a total of 64 sector regions, i.e., 0^(th)-63^(rd) sectorregions (210-0 through 210-63).

The sixty four sector regions 210 are provided by dividing the memorycell array region 200 in the second direction (row direction) B asindicated in FIG. 3(A), and each of the sector regions 210 has alongitudinally oblong configuration with the first direction (columndirection) A being its longer side direction. The minimum unit to erasedata is the sector region 210, and data stored in the sector region 210may be erased all together or in a time sharing manner.

The memory cell array regions 200 includes, for example, 4K word linesWL, and 4K bit lines BL. In the present embodiment, one bit line SBL isconnected to two MONOS memory elements 108A and 108B, and therefore 4Ksub-bit lines SBL means a storage capacity of 8 Kbit. Each of the sectorregions 210 has a storage capacity equivalent to {fraction (1/64)} ofthe entire storage capacity, which is a storage capacity defined by (4Kword lines WL)×(64 bit lines BL)×2.

FIG. 3(B) shows details of two adjacent ones of the sector regions 210,e.g., the 0^(th) and 1^(st) sector regions, in the non-volatilesemiconductor memory apparatus shown in FIG. 3(A). As shown in FIG.3(B), local driver regions (including local control gate driver, localbit line selection driver and local word line driver) 220A and 220B aredisposed on both sides of the two sectors 210. Also, a sector controlcircuit 222 is disposed, for example, along upper sides of the twosectors 210 and the two local driver regions 220A and 220B.

Each of the sector regions 210 is divided in the second direction sothat it has 16 memory blocks 214 for I/O 0 through I/O 15 (i.e., memoryblocks corresponding to the respective I/O bits) that allow 16-bit datato be read or written. Each of the memory blocks 214 includes 4K (4096)word lines WL, as indicated in FIG. 3(B).

As indicated in FIG. 3(C), each of the sector regions 210 shown in FIG.3(B) is divided into 8 large blocks 212 in the first direction A. Eachof the large blocks 212 is divided into 8 small blocks 215 in the firstdirection A, as indicated in FIG. 3(D).

Each of the small blocks 215 includes 64 word lines WL, as indicated inFIG. 3(E). Also, each of the small blocks 215 is formed of 16 smallmemory blocks 216 arranged along the row direction.

FIG. 4 shows a circuit diagram of a concrete structure of the smallmemory block 216 shown in FIGS. 3(A)-3(E).

In FIG. 4, the twin memory cell 100 has a transistor T2 that is drivenby the word gate 104 and transistors T1 and T3 that are respectivelydriven by the first and second control gates 106A and 106B, which areserially connected to one another. The small memory block 216 is formedby arranging, for example, 64 twin memory cells 100 in the columndirection and, for example, 4 twin memory cells 100 in the rowdirection, and includes 64 word lines WL, 4 sub-control gate linesSCG0-SCG3, and 4 bit lines BL0-BL3.

All the word gates 104 in each of the rows are commonly connected to theword line WL in each of the rows. The mutually adjacent first and secondcontrol gates 106A and 106B of the twin memory cells 100 that arearranged adjacent to one another in the row direction are connected tocommon sub-control gate lines SCG0-SCG3, which are shared by the twinmemory cells 100 in the same column. Also, the mutually adjacentimpurity layers 110 of the twin memory cells 100 that are arrangedadjacent to one another in the row direction are connected to common bitlines BL0-BL3, which are shared by the twin memory cells 100 in the samecolumn.

The small memory block 216 is the minimum control unit to read andprogram operations. Four of the word gates 104 in one of the rows areselected by the 64 word lines WL, one of the rows selected by settingthe 4 sub-control gate lines SCG0-SCG4 with specified voltages, and oneof the 8 memory elements 108A and 108B in the row direction in theselected row is selected as a selected memory element. In other words,one (1 bit) of the 8 memory elements in the row direction can beselected as a selected memory element, which can be read or programmedby the bit line BL.

FIG. 5 is a schematic of a concrete structure of the sector 210.

As described above, the sector 210 is formed of 16 memory blocks 214arranged in the row direction, in other words, 64 small memory blocks216 arranged in the column direction. All of the sub-control gate linesSCG0-SCG3 of the 16 small memory blocks 216 arranged in the rowdirection are respectively commonly connected to one another to composemain control gate lines MCG0-MCG3, respectively.

The main control gate lines MCG0-MCG3 of the small blocks 215 (215-0through 215-63) are connected to a CG driver 300 (300-0 through 300-63).The CG driver 300 is a control gate driver section for each unit of thesector 210, and controls the main control gate lines MCG0-MCG3, tothereby set voltage levels of the sub-control gate lines SCG0-SCG3 ofthe small blocks 215 (memory blocks 216).

One of the 64 small blocks 215 is selected as a selected block, and areading and programming operation is performed for a selected memoryelement within the selected block in bits. When there is a selectedblock in one of two adjacent sectors, a small block 215 in the otheradjacent sector is called an opposing block.

FIG. 6 is a schematic of a structure of each driver that controls one ofthe small blocks 215 in the 0^(th) sector and an opposing small block215 in the 1^(st) sector. FIG. 6 shows details of the two small blocks215 within the adjacent two sectors, the 0^(th) and 1^(st) sectors 210,and local driver regions 220A and 220B disposed on both sides of thesmall blocks 215. It is noted that the 2^(nd) sector, 3^(rd) sector,4^(th) sector, 5^(th) sector, . . . have the same structure as the oneshown in FIG. 6.

As indicated in FIG. 6, in the local driver region 220A on the left sideof the FIG., 0^(th) through 3^(rd) local control gate line drivers(CGDRV0-CDGRV3) are disposed. The four local control gate line driversCGDRV0-CDGRV3 in FIG. 6 form one CG driver 300 shown in FIG. 5. Thelocal control gate line drivers CGDRV0-CDGRV3 control each of thesub-control gate lines SCG0-SCG3 in each of the small memory blocks 216within the small block 215.

Also, the local driver region 220A within the 0^(th) sector is providedwith 0^(th), 2^(nd), . . . , and 62^(nd) local word line drivers(WLDRV0, WLDRV2, . . . , and WLDRV62) that drive even numbered wordlines WL0, WL2, . . . , and WL62 in the 0^(th) and 1^(st) sectors,respectively. Similarly, the local driver region 220B within the 1^(st)sector is provided with 1^(st), 3^(rd), . . . , and 63^(rd) local wordline drivers (WLDRV1, WLDRV3, . . . , and WLDRV63) that drive oddnumbered word lines WL1, WL3, . . . , and WL63 in the 0^(th) and 1^(st)sectors, respectively. The local driver regions 220A and 220B are alsoprovided with a redundant word line driver (WLDRVR) (not shown) thatdrives one redundant word line within the 0^(th) sector.

The local word line drivers (WLDRV0 through WLDRV63) are controlled bythe global WL decoder 201 shown in FIGS. 3(A)-3(E) and are capable ofselecting the word gates 104 in each of the rows of the 0^(th) and1^(st) sectors in units of rows. Also, with the local control gate linedrivers (CGDRV0 through CGDRV3), one of the memory elements of the twinmemory cell in a specified column can be selected in units of memoryelements for each sector.

Also, the local driver regions 220A and 220B are provided with 0^(th)and 1^(st) local bit line drivers (BSDRV0 and BSDRV1) disposed therein,respectively. The 1^(st) first local bit line driver (BSDRV1) drives bitline selection transistors 217A (see FIG. 7) that control whether or notodd numbered bit lines BL1 and BL3 in the 0^(th) and 1^(st) sectors areto be connected to the main bit lines in units of small blocks 215. The0^(th) local bit line driver (BSDRV0) drives bit line selectiontransistors 217B (see FIG. 7) that control whether or not even numberedbit lines BL0 and BL2 in the 0^(th) and 1^(st) sectors are to beconnected to the main bit lines in units of small blocks 215.

FIG. 7 shows a circuit diagram of a concrete structure of the smallblocks 215 arranged adjacent to one another in the 0^(th) and 1^(st)sectors. Other pairs of adjacent sectors have the same structure.

The bit lines BL (BL0-BL3) are disposed in each of the small memoryblocks 216 independently from one another, as indicated in FIG. 4. Thebit lines BL0 (impurity layers) in the respective small memory blockswithin an I/O memory block, and also the bit lines BL1, BL2 and BL3, aremutually, commonly connected by metal wirings to form a main bit lineMBL. A bit line selection transistor 217A is disposed in each path thatleads from each of the main bit liens MBL to each of the bit lines BL1and BL3 in the small memory blocks 216, and a bit line selectiontransistor 217B is disposed in each path that leads to each of the bitlines BL0 and BL2 in the small memory blocks 216.

Paths for signal input and output of each of the I/O memory blocks arefour main bit lines MBL, and the four bit line selection transistors217A and 217B are turned on by the local bit line drivers (BSDRV0 andBSDRV1) to make each of the bit lines BL active, and voltage applicationand current supply to each of the bit lines BL are controlled to enablereading and programming operations in units of 1 bit.

As indicated in FIG. 6 and FIG. 7, the word lines WL are shared by the0^(th) sector and the 1^(st) sector, but the main bit lines MBL and maincontrol gate lines MCG are provided independently from one another.

(Driver Circuits in 0^(th) and 1^(st) Sectors)

Next, referring to FIG. 1, circuits that drive the twin memory cellswithin each of the small blocks 215 in the 0^(th) and 1^(st) sectors aredescribed.

First, as components that are shared by the 0^(th) through 63^(rd)sectors, there are provided a control logic 53, a voltage generationcircuit 55, a pre-decoder 400, 64 global decoders 402-0 through 402-63,and a Y decoder 404. The control logic 53 is provided with a variety ofcontrol inputs, and generates a variety of control signals includingcontrol signals for the voltage generation circuit 55.

The pre-decoder 400 decodes address signals A[20-0] that specifynon-volatile memory elements subject to selection (selected cells).Table 1 below shows meanings of the address signals A[20-0].

TABLE 1 Address Group Function A[20-15] Sector Choose 1 of 64 A[14-12]Row Choose 1 of 8 A[11-0] Choose 1 of 4096 A[11-9] Large Block Choose 1of 8 A[8-6] Small Block Choose 1 of 8 A[5-0] Column Choose 1 of 64

As indicated in Table 1 above, one sector among the 64 sectors isselected with the upper address signal A[20-15], one bit among 4 cells(8 bits) in one small memory block 216 shown in FIG. 4 is selected withthe intermediate address signal A[14-12], and one word line WL among the4096 word lines is selected with the lower address signal A[11-0]. Also,one of the 8 large blocks 212 existing in one sector is selected withthe address signal A[11-9], one of the 8 small blocks 215 existing inone large block 212 is selected with the address signal A[8-6], and oneof the 64 word lines WL existing in one small block 215 is selected withthe address signal A[5-0].

The 64 global decoders 402-0 through 402-63 activate the 64 global wordlines GWL[0] through GWL[63] based on the results of pre-decoding thelower address signal A[11-0] by the pre-decoder 400. At the time of datareading and data programming, only one of the global word lines GWL ismade active (at Vdd). At the time of data erasing, when data in onesector are erased all together, all of the 64 global word lines GWL aremade active (at Vdd), to thereby select all of the word lines within onesector, and a word line voltage for data erasing is supplied. Also, allof the control gate lines within one sector are selected, and a controlgate voltage for data erasing is supplied.

The Y decoder 404 drives Y pass circuits 412 via a Y pass selectiondriver 410, and connect bit lines selected within the small blocks 215to sense amplifiers or bit line drivers in the succeeding stage.

As described above, the local driver regions 220A and 220B are providedon right and left sides of each of the small blocks 215 shown in FIG. 7.

For example, in the case of the small block 215-0 in the first rowwithin the 0^(th) and 1^(st) sectors, there are provided in the localdriver region 220A on the left side of the small block 215-0 the controlgate line drivers CGDRV that drive the four main control gate lines MCGof the small block 215-0 in the first row within the 0^(th) sector, inother words, the local CG drivers CGDRV 0-3, the local word line driversWLDRV [31-0] that drive the even numbered 32 word lines WL within the0^(th) and 1^(st) sectors, and a local control gate line selectiondriver CSDRV [0] that drives the bit line selection transistors 217Bthat are connected to the odd numbered sub-control gate lines SCG 1, 3,. . . , and 63 in the 0^(th) and 1^(st) sectors. In the local driverregion 220B on the right side, there are provided the control gate linedrivers CGDRV that drive the four main control gate lines MCG of thesmall block 215-0 in the first row within the 1^(st) sector, in otherwords, the local CG drivers CGDRV 0-3, the local word line drivers WLDRV[63-32] that drive the odd numbered 32 word lines WL within the 0^(th)and 1^(st) sectors, and a local control gate line selection driver CSDRV[1] that drives the bit line selection transistors 217A that areconnected to the even numbered sub-control gate lines SCG 0, 2, . . . ,and 62 in the 0^(th) and 1^(st) sectors.

In the present embodiment, the cell array block uses twin memory cells.Therefore, as described below, to perform data reading operation, dataprogramming operation and data erasing operation by driving the cellarray, plural kinds of voltages need to be supplied in each of theoperations in addition to the erasing operation. The voltage generationcircuit 55 is controlled by the control logic 53 and generates pluralkinds of voltages that are to be used for the memory cell array block.

Next, descriptions are provided as to data reading operation, dataprogramming operation and data erasing operation for the memory cellarray region 200 using voltages provided from the voltage generationcircuit 55.

For data reading and data programming operations, the control isperformed in units of two adjacent ones of the sectors 210, e.g., an oddnumbered sector and an even numbered sector. FIG. 8 describes thecontrol for two sectors. Each rectangular frame in FIG. 8 indicates asmall block row. A column of small block rows on the left side indicatesone sector (the 0^(th) sector in the example shown in FIG. 8), and acolumn of small block rows on the right side indicates a sector (1^(st)sector) adjacent to the 0^(th) sector.

A selected block is a selected small block row, and an opposing block isa non-selected small block row adjacent to the selected block. Smallblock rows with hatched lines in FIG. 8 indicate all non-selected blocksother than the selected block and the opposing block.

Table 2 and Table 3 below show potentials on the respective control gatelines CG, bit lines BL and word lines WL at the time of reading,programming and erasing operations.

Referring to Table 2 and Table 3, each of the operation modes isdescribed below. The description of the operations shall be providedwith one twin memory cell 100 being typified to have a transistor T2driven by the word gate 104 and transistors T1 and T3 respectivelydriven by the first and second control gates 106A and 106B, which areserially connected to one another, as shown in FIG. 9.

TABLE 2 Selected Block Selected Twin MONOS Cell Opposing Selected Mem-Memory Non-selected Twin MONOS ory element element Cell Mode BS WL BL CGBL CG WL BL CG Read 4.5 V Vdd 0 V 1.5 V ± Sense 3 V Vdd Sense 3 VOpposing 0.1 V or 0 V or 0 V or 1.5 V ± Side or 0.1 V Vdd or 0 VSelected Side Program 8 V About 5 V 5.5 V 1 prg = 2.5 V About 5 V 5.5 V1 V 5 μA 1 V or Vdd or 2.5 V (0 to or 0 V or (0 to or 0 V 1 V) 1 V)Erase 8 V 0 V 4.5 to −1 to 4.5 to −1 to 5 V −3 V 5 V −3 V

TABLE 3 Opposing Block Non-selected Block Mode BS WL BL CG BS WL BL CGRead 4.5 V Vdd 0 V 0 V 0 V 0 V F 0 V Opposing or 0 V side Vdd Selectedside Pro- 8 V About 0 V 0 V 0 V 0 V F 0 V gram 1 V or 0 V Erase 8 V 0 V0 V 0 V 0 V 0 V F 0 V

First, operations in a data read mode when data is read from the memorycell are described with reference to the schematics of FIG. 10 and FIG.11, the graph of FIG. 12, and the schematics of FIG. 13 and FIG. 14. InFIG. 10, a twin memory cell 100 [i] that is connected to one word lineWL is defined as a selected cell, and the side of a MONOS memory element108B adjacent to the word gate 104 of the selected cell is defined as aselected side. FIG. 10 shows potentials set at various locations whendata is read out in a reverse mode from the selected memory element108B. FIG. 10 indicates potentials set at various locations in theselected cell and in twin memory cells 100 [i−1] through 100 [i+2] thatare non-selected cells adjacent to the selected cell. Also, FIG. 11indicates set voltages in the selected cell. The opposite side of theselected memory element among the memory elements in the selected cellis defined as an opposing side, and the memory element on the opposingside is defined as an opposing memory element.

As indicated in FIG. 11, in the twin memory cell 100 [i] in FIG. 10 thatis a selected cell, it is assumed that the word gate 104 is connected tothe word line WL1 in the second row in the memory block 214. In thiscase, Vdd (for example, 1.8V) is applied as a read word line selectionvoltage to the word line WL1. As a result, all of the transistors T2 inthe twin memory cells in the second row are turned on. 0V is applied tothe other word lines WL0, WL3, WL4, . . .

The constant voltage circuit 18 supplies 3V as a voltage VPCGH to thelocal control gate line drivers (CGDRV0 through CGDRV3) which thensupply the same as an override voltage through the sub-control gate lineSCG [i] to the control gate 106A on the opposing side of the twin memorycell 100 [i]. Also, the constant voltage circuit 16 supplies 1.5V as avoltage VPCGL to the local driver region 220A which then reads out the1.5V and supplies the same as a voltage Vread to the control gate 106Bon the selected side of the twin memory cell 100 [i] as a gate voltageVCG.

The override potential is a potential that is required to turn on atransistor corresponding to the opposing memory element and to flowprogramming current without regard to the presence or absence ofprogramming of the opposing memory element in the twin memory cell 100[i].

By the override voltage applied to the control gate 106A on the opposingside, the transistor T1 corresponding to the MONOS memory element 108Ais turned on. In this case, the operation of the transistor T3corresponding to the MONOS memory element 108B differs depending onwhether or not charge is stored in the MONOS memory element 108B that isthe selected cell.

FIG. 12 shows the relationship between gate voltages VCG for the controlgate on the selected side which are indicated along the horizontal axisand currents Ids that flow between the source and the drain of thetransistor corresponding to the selected memory element which areindicated along the vertical axis.

As shown in FIG. 12, when no charge is stored in the MONOS memoryelement 108B that is the selected memory element, the current Ids startsflowing when the control gate voltage VCG exceeds a low thresholdvoltage Vlow. In contrast, when charge is stored in the MONOS memoryelement 108B that is the selected memory element, the current Ids doesnot start flowing unless the control gate voltage VCG on the selectedside exceeds a high threshold voltage Vhigh.

A voltage Vread that is applied to the control gate 106B on the selectedside at the data reading operation is set generally intermediate the twothreshold voltages Vlow and Vhigh. Accordingly, when no charge is storedin the MONOS memory element 108B that is the selected memory element,the current Ids flows; and when charge is stored in the MONOS memoryelement 108B that is the selected memory element, the current Ids doesnot flow.

At the time of data reading operation, the bit line BL [i] (impuritylayer 110 [i]) that is connected to the opposing memory element isconnected to the sense amplifier 24, as indicated in FIG. 11. Also,potentials VD [i−1], [i+1] and [i+2] of the other bit lines BL [i−1],[i+1] and [i+2] are set at 0V, respectively. By dosing so, when nocharge is stored in the MONOS memory element 108B that is the selectedmemory element, the current Ids flows, and a current of, for example, 25μA or greater flows to the bit line BL [i] on the opposing side throughthe transistors T1 and T2 that are in an ON state. In contrast, whencharge is stored in the MONOS memory element 108B that is the selectedmemory element, the current Ids does not flow, and a current that flowsto the bit line BL [i] that is connected to the opposing memory elementis, for example, less than 10 nA even when the transistors T1 and T2 arein an ON state.

In this manner, by detecting the current that flows in the bit line BL[i] of the opposing side, data can be read from the MONOS memory element108B of the twin memory cell 100 [i], which is the selected memoryelement.

By the bit line selection transistor (n-type MOS transistor) 217A, thebit lines BL [i] and [i+2] become active; and by the bit line selectiontransistor 217B, the bit lines BL [i−1] and [i+1] become active.

It is difficult to provide the selection transistors 217A and 217B witha high current drivability due to the size limitation. In accordancewith the present embodiment, they are provided with, for example, achannel width W=0.9 μm, and a channel length L=0.8 μm.

Since it is necessary to secure the aforementioned current on the bitline BL [i] that is connected to the sense amplifier 24, the gatevoltage of the bit line selection transistor 217A is set at a highvoltage, for example, 4.5V by the constant voltage circuit 14.

In the mean time, the voltage on the source side of the MONOS memoryelement 108A on the selected side in FIG. 11 reaches a voltage of about0V (about several ten-several hundred mV). For this reason, the backgate of the bit line selection transistor 217B has few impact, andtherefore its gate voltage is set at Vdd. As a voltage of 4.5V does nothave to be supplied to the gate of the bit line selection transistor217B, the load on the voltage generation circuit 55 (strong charge pump11) can be reduced.

Non-selected cells within the selected block are set at voltage valuesindicated in Table 2 above.

FIG. 13 describes voltages set in the opposing block in a data read modewhen data is read from the memory cell.

In the opposing block in the first sector, voltages indicated in Table 3above are set. In other words, as indicated in FIG. 13, since thevoltage on each of the word lines WL and the gate voltage of the bitline selection transistors are shared in the 0^(th) and 1^(st) sectors,the same voltage values as those in the selected block indicated in FIG.11 are set. All of the bit lines BL0-BL3 are set at 0V.

FIG. 14 indicates a voltage setting state in non-selected blocks (smallblocks 215) that exist in the 0^(th) through 63^(rd) sectors other thanthe selected block and opposing block. The voltage setting indicated inTable 3 above is also applied to each of the non-selected blocks shownin FIG. 13.

In these non-selected blocks, the gate voltage of the bit line selectiontransistors 217A and 217B, the word lines WL and the control gate linesCG are all set at 0V. As the bit line selection transistors 217A and217B are off, the bit lines BL are placed in a floating state.

Next, operations that take place at the time of programming twin memorycells are described with reference to the schematics of FIGS. 15 through20.

In FIG. 15, a twin memory cell 100 [i] that is connected to one wordline WL is defined as a selected cell, the side of a MONOS memoryelement 108B adjacent to the word gate 104 of the selected cell isdefined as a selected side, and FIG. 15 shows potentials set at variouslocations when data programming is performed for the selected memoryelement 108B. FIG. 16 indicates potentials set at various locations inthe selected block. A data erasing operation to be described below isperformed before the data programming operation.

As indicated in FIG. 15, in a manner similar to FIG. 10, the potentialon the sub-control gate line SCG [i] is set at an override potential(2.5V) by using an output of the constant voltage circuit 16, and thepotential on the sub-control gate lines SCG [i−1] and [i+2] is set at0V.

Also, the potential on each of the word gates 104 in FIG. 16 is set at aprogramming word line selection voltage of about 1.0V that is lower thanthe power supply voltage Vdd by the word line WL1 based on an output ofthe word gate voltage generation circuit 20. Also, a write voltageVwrite (See Table 2 (5.5V)) that is a programming control gate voltageis applied to the control gate 106B of the selected memory element ofthe twin memory cell 100 [i] through the sub-control gate line SCG [i+1]by using an output of the constant voltage circuit 18.

To control BL selection in units of sectors, a Y pass circuit isprovided for each sector for the bit lines BL that are I/O paths of thememory element as described above. With the Y pass circuit, input andoutput of the bit lines BL can be controlled in units of sectors.

FIG. 17 schematically shows the interior of such a Y pass circuit 412that is connected to the bit line BL. It is noted that the circuit shownin FIG. 17 corresponds to a transistor Q9 shown in FIG. 25 to bedescribed below.

The Y pass circuit 412 includes therein a first transistor 441 thatconnects the bit line BL to the sense amplifier 24, and a secondtransistor 442 that connects it to another path. Signal YS0 and itsinverted signal/YS0 are input in gates of the first and secondtransistors 441 and 442, respectively.

The source of the second transistor 442 connects to a constant currentsource 444 through a switch 443. The switch 443 flows 5 μA at the timeof writing “0”, and connects to Vdd at the time of writing “1”.

At the time of programming, the first transistor 441 is turned on by thesignal YS0, the bit line BL [i+1] is connected to the bit line driverthrough the transistor 441, and the voltage VD [i+1] of the bit line BL[i+1] is set at a programming bit line voltage that is, for example, 5V,as indicated in FIG. 15 and FIG. 16. The voltage of 5V is obtained froma voltage VPBL of 5.2V that is generated by the constant voltage circuit13.

In the mean time, the second transistor 442 in the Y pass circuit 412,which is connected to the BL [i+2], is turned off by the signal/YS0, andthe switch 443 selects the power supply voltage Vdd, such that the bitline BL [i+2] is set at the voltage Vdd.

By the Y pass circuit 412 that connects to the bit lines BL[i−1] and[i], a current from the constant current source 444 flows through thesecond transistor 442 and the switch 443 to the bit lines BL [i−1] and[i]. It is noted that the MONOS cell that connects to the bit line BL[i−1] is turned off as its control gate line CG [i−1] is at 0V.Accordingly, no current flows in the MONOS cell, and the bit line BL[i−1] is set at 0V through the constant current source 444.

With this setting, the transistors T1 and T2 of the twin memory cell 100[i] are both turned on, and while the current Ids flows toward the bitline BL [i], channel hot electrons (CHE) are trapped in the ONO film 109of the MONOS memory element 108B. In this manner, the programmingoperation is performed for the MONOS memory element 108B, and data “0”is written.

Here, there is also another method in which the programming word lineselection voltage is set at about 0.77V instead of about 1V, and the bitline BL [i] is set at 0V. In the present embodiment, while theprogramming word line selection voltage is raised to about 1V toincrease the source-drain current, the current that flows into the bitline BL [i] at programming is controlled by the constant current source444. As a result, the voltage on the bit line BL [i] can be optimallyset (in a range between 0V and 1V, and about 0.7V in the presentembodiment), and therefore the programming operation can be optimallyperformed.

In the aforementioned operation, a voltage of 5.5V provided based on theoutput of the constant voltage circuit 18 is also applied to the controlgate of the non-volatile memory element 108A on the left side of thetwin memory cell 100 [i+1] that is a non-selected cell. In this casealso, the voltage applied to the control gate CG [i+2] on the right sideof the twin memory cell 100 [i+1] is 0V, and therefore no current flowsbetween the source and the drain (between bit lines) of the twin memorycell 100 [i+1]. However, since a voltage of 5V is applied to the bitline BL [i+1], punch through current may flow and write disturb mayoccur if a high electric field is applied across the source and drain(bit lines) of the twin memory cell 100 [i+1].

Therefore, the voltage on the bit line BL [i+2] is set at Vdd, forexample, instead of 0V, to thereby reduce a potential difference acrossthe source and drain to prevent write disturb. Also, by setting thevoltage on the bit line BL [i+2] at a voltage value exceeding 0V, andpreferably a voltage value equivalent to or greater than a word lineselection voltage at the time of programming, the transistor T2 of thememory cell [i+1] becomes difficult to turn on. Accordingly, this canalso reduce or prevent disturbs.

Also, since a voltage of 5V needs to be supplied to the bit line BL[i+1], a voltage of 8V is applied to the gate of the bit line selectiontransistor 217B by a BL_select driver 21. In the mean time, a voltage of8V is also applied to the gate of the bit line selection transistor217A. Because of the need to set the bit line BL [i+2] at Vdd for thereasons described above, a voltage higher than Vdd also needs to beapplied to the gate of the transistor 217A, and therefore the voltage of8V that is the same as the gate voltage of the transistor 217B is used.The gate voltage of the bit line selection transistor 217A may be anylevel higher than Vdd+Vth.

The voltage setting indicated in Table 2 is applied to non-selectedmemory elements within the selected block.

In the opposing block in the 1^(st) sector, the voltage settingindicated in Table 3 above is applied. More specifically, as indicatedin FIG. 18, since the voltage on each of the word lines WL and the gatevoltage of the bit line selection transistors are shared in the 0^(th)and 1^(st) sectors, the same voltage values as those in the selectedblock indicated in FIG. 15 are set. All of the bit lines BL0-BL3 are setat 0V.

FIG. 19 indicates a voltage setting state in non-selected blocks (smallblocks 215) that exist in the 0^(th) through 63^(rd) sectors other thanthe selected block and opposing block. The voltage setting indicated inTable 3 above is also applied to each of the non-selected blocks shownin FIG. 19.

In these non-selected blocks, the gate voltage of the bit line selectiontransistors 217A and 217B, the word lines WL and the control gate linesCG are all set at 0V. As the bit line selection transistors 217A and217B are off, the bit lines BL are placed in a floating state.

FIG. 20 indicates potentials set at various locations in the twin memorycells 100 [i−1], 100 [i] and 100 [i+1] when the MONOS memory element108A on the left side of the twin memory cell 100 [i] is programmed.

Next, operations at the time of erasing data of twin memory cells aredescribed with reference to the schematics of FIGS. 21 through 24.

FIG. 21 indicates potentials set at various locations when data at allof the memory cells within the 0^(th) sector are erased all together.FIG. 22 indicates voltages set at part of memory cells within the 0^(th)sector.

As indicated in FIG. 21 and FIG. 22, at the time of data erasing, 0V isselected by the decoder, and the potential of each of the word gates 104is set at 0V by the word line WL; and the potential of the control gates106A and 106B is set at an erasing control gate line voltage of, forexample, about −1V to −3V by the sub-control gate lines SCG [i−1], [i],[i+1] and [i+2], by using the output of a negative charge pump 26.Further, each of the potentials on the bit lines BL [i−1], [i], [i+1]and [i+2] is set at a erasing bit line voltage of, for example, about4.5V to 5V by the bit line selection transistors 217A and 217B and thebit line drivers, by using the outputs of the constant voltage circuits13 and 14.

In this case, the tunnel effect is generated by the erasing control gateline voltage applied to the control gates and the erasing bit linevoltage applied to the bit lines, electrons that have been trapped inthe ONO film 109 of each of the MONOS memory elements 108A and 108B aretransferred and erased from the ONO films 109. In this manner, data inthe memory elements of a plurality of twin memory cells simultaneouslybecome “1” such that the data is erased.

As an erasing operation which may be different from the above, hot holesmay be formed by band-band tunneling on the surface of the impuritylayer which defines a bit, to thereby erase electrons that have beenstored.

Also, without being limited to the operation of erasing data within onesector all together, data may be erased in a time sharing manner.

In the opposing blocks within the 1^(st) sector, the voltage settingindicated in Table 3 is applied. More specifically, as indicated in FIG.23, since the voltage on each of the word lines WL and the gate voltageof the bit line selection transistors are shared in the 0^(th) and1^(st) sectors, the same voltage values as those in the selected blockindicated in FIG. 19 are set. All of the bit lines BL0-BL3 are set at0V.

Since the control gate line CG and the bit line BL are both at 0V, nodisturb is generated in any of the cells within the opposing blocks.

FIG. 24 indicates a voltage setting state in non-selected blocks (smallblocks 215) that exist in the 0^(th) through 63^(rd) sectors other thanthe selected block and opposing block. The voltage setting indicated inTable 3 above is also applied to each of the non-selected blocks shownin FIG. 24.

In these non-selected blocks, the gate voltage of the bit line selectiontransistors 217A and 217B, the word lines WL and the control gate linesCG are all set at 0V. As the bit line selection transistors 217A and217B are off, the bit lines BL are placed in a floating state.

However, the voltage on the bit lines BL is close to almost 0V, and nodisturb is generated in any of the cells within the non-selected blocks.

FIG. 25 is a schematic of a concrete structure of the voltage generationcircuit 55 indicated in FIG. 1. In FIG. 25, for the simplification ofthe drawing, various drivers and signal lines are represented by singlecorresponding components, respectively, and connection relations aresimplified to clarify the voltage generation sources and their supplydestinations. In FIG. 25, . . . V@Standby, . . . V@Read, . . . V@Pgm,and V@Ers indicate voltages at the time of standby mode, read mode,program mode and erase mode, respectively.

In the present embodiment, by using one charge pump, a plurality oftypes of voltages required to provide memory reading, programming anderasing operations can be simultaneously generated.

Referring to FIG. 25, a strong charge pump 11 generates plural kinds ofvoltages from one power supply source Vdd. FIG. 26 is a schematic of aconcrete structure of the strong charge pump 11 shown in FIG. 25.

The strong charge pump 11 is formed from an oscillation circuit 32, acharge pump circuit 34 and a level sensor 33. The oscillation circuit 32outputs an oscillation output of a specified frequency to the chargepump circuit 34. The charge pump circuit 34 performs step-up processingwith its charge pump operation for the oscillation output to therebygenerate stepped-up voltages. The level sensor 33 detects levels ofoutput voltages of the charge pump circuit 34 and controls theoscillation of the oscillation circuit 32 such that its level is at aspecified value. By this, the strong charge pump 11 is capable ofgenerating voltages at specified levels.

In accordance with the present embodiment, the strong charge pump 11steps up the power supply voltage Vdd of 1.8V, for example, to generate5.0V at reading operations, and 8.0V at programming and erasingoperations depending on the operational conditions of the memory cellarray.

A pool capacitor 27 is provided between an output terminal of the strongcharge pump 11 and the reference voltage point. The pool capacitor 27pools an output of the strong charge pump 11. In the present embodiment,the capacity of the pool capacitor 27 is set at a relatively smallvalue.

The output of the strong charge pump 11 (the retained voltage of thepool capacitor 27) is supplied to constant voltage circuits 13-18, whichare formed from regulators RG1-RG6 and transistors Q1-Q6. FIG. 27 showsa circuit diagram of the constant voltage circuit 13 shown in FIG. 25.The structure of the other constant voltage circuits 14-18 is the sameas that of the constant voltage circuit 13.

A voltage from the strong charge pump 11 is supplied to a terminal 35. Aspecified reference voltage Vref is applied to a positive polarity inputterminal of a differential amplifier 40. An output terminal of thedifferential amplifier 40 connects to a gate of a p-type MOS transistorQ1. A source of the transistor Q1 connects to the terminal 35, and adrain thereof connects to a negative polarity input terminal of thedifferential amplifier 40. Also, the drain of the transistor Q1 connectsto a reference potential point through a resistor R1 and a variableresistor VR1. The differential amplifier 40, the resistor R1 and thevariable resistor VR1 form the regulator 13 shown in FIG. 25.

The transistor Q1 functions as a variable resistance element, and thedifferential amplifier 40 changes its output to make a differencebetween its two inputs to be “0”. As a result, the voltage of the drainof the transistor Q1 coincides with the reference voltage Vref. Voltagesappearing on an output terminal 36 have values in which the referencevoltage Vref is resistance-divided with the resistance R1 and thevariable resistance VR1. By appropriately setting resistance values ofthe variable resistance VR1, plural kinds of voltages can be generatedas outputs of the constant voltage circuit 13.

As indicated in FIG. 25, in accordance with the present embodiment, theconstant voltage circuit 13 can generate 5.2V or the power supplyvoltage Vdd as an output voltage VPBL. Also, the constant voltagecircuit 14 can generate 5.0V, 4.5V or 8.0V as an output voltage VPYS.The voltage VPBL from the constant voltage circuit 13 is supplied to aBL driver 23, and the voltage VPYS from the constant voltage circuit 14is supplied to a BL_select driver 21 and a Y_select driver 22.

As a voltage VPCGL to be described below, a voltage of the power supplyvoltage Vdd (1.8V) or lower may be used. Accordingly, the constantvoltage circuit 15 steps down the power supply voltage Vdd to generate1.5V, 1.3V or a voltage Vdd as the voltage VPCGL, and supplies the sameto a CG decoder/driver 25. Also, a voltage PCGL is supplied to the CGdecoder/driver 25 from the constant voltage circuit 16.

An output terminal of the constant voltage circuit 15 connects to ap-type MOS transistor Q7. A gate of the transistor Q7 connects to a HVSW(high voltage switch) 19. The power supply voltage is supplied from thestrong charge pump 11 to the HVSW 19; and the application of a highlevel (hereafter referred to as “H”) voltage to the transistor Q7 canturn off the transistor Q7. With this, when a voltage that is higherthan the power supply voltage Vdd is supplied as the voltage VPCGL fromthe constant voltage circuit 16, the transistor Q7 can be turned off toprevent the current from flowing into the constant voltage circuit 15.

It is noted that the constant voltage circuit 16 can generate 1.5V,2.5V, a voltage Vdd, 1.8V or 1.3V as an output voltage VPCGL.

Also, the constant voltage circuit 18 operates in an active mode, andcan generates 3.0V or 5.5V as an output voltage VPCGH.

In the present embodiment, the constant voltage circuit 17 is providedin parallel with the constant voltage circuit 18. The constant voltagecircuit 18 consumes currents on the order of several hundred μA, forexample, when it supplies a generated voltage VPCGH. On the other hand,the constant voltage circuit 17 is set by appropriately setting valuesof the differential amplifier 40, resistance R1 and variable resistanceVR1 (see FIG. 27) such that it consumes currents on the order of severalμA, for example, when it supplies a generated voltage. The constantvoltage circuit 17 operates in all the modes including the standby mode,and generates a voltage close to a voltage required at the time ofreading as a voltage VPCGH (for example, 2.5V).

The BL driver 23 corresponds to a BL driver section in the senseamplifier and the BL driver shown in FIG. 1. The BL driver 23 uses avoltage VPBL supplied from the voltage generation circuit 50 to generatea voltage of 5.2V at the time of programming and erasing.

The BL_select driver 21 corresponds to a local bit line driver (BSDRV0,BSDRV1) in FIG. 6. The BL_select driver 21 receives a voltage VPYS, andapplies to the gate of the transistor Q8 a voltage of 4.5V at the timeof reading, 8.0V at the time of programming, and 8.0V at the time oferasing. The transistor Q8 corresponds to the bit line selectiontransistor 217A or 217B in FIG. 7. As described above, one small blockis provided with each two (a total of four) bit line selectiontransistors 217A and 217B, that can activate each of the bit linesBL0-BL3.

The Y_select driver 22 and the transistor Q9 correspond respectively tothe Y pass selection driver 410 and the Y pass circuit in FIG. 1. Inother words, the Y_select driver 22 receives a supply of a voltage VPYSfrom the voltage generation circuit 55 through the Y decoder 404, andapplies to the gate of the transistor Q9 a voltage of 4.5V at the timeof reading, 8.0V at the time of programming, and 8.0V at the time oferasing.

The transistor Q9 forms a switch within the Y pass circuit 412 in FIG.1. One of the source and drain of the transistor Q9 connects to thetransistor Q8 through the BL terminal, and the other connects to thesense amplifier 24 and the BL driver 23. The BL driver 23 can apply avoltage of 5.2V to the bit lines BL through the transistors Q9 and Q8.In this manner, a voltage of 5V can be applied to each of the bit linesBL by the voltage generation circuit 55.

A negative charge pump 26 outputs as a voltage VNCG a voltage of −3V ora ground potential GND to the CG decoder/driver 25. The CGdecoder/driver 25 corresponds to the local control gate line driver(CGDRV0-CGDRV3) in FIG. 6, and outputs of the CG decoder/driver 25 aresupplied to four main control gate lines (MCG0-MCG3) of the small blockrow. Voltages VPCGL and VPCGH from the voltage generation circuit 55 aresupplied to the local control gate line drivers (CGDRV0-CGDRV3) throughcontrol gate line drivers (CGdrv0-CGdrv7). The CG decoder/driver 25 iscapable of supplying the inputted voltages VPCGL and VPCGH independentlyto each of the main control gate lines.

A word gate voltage generation circuit 20 generates as a voltage VPWL avoltage of 1.0V or a ground potential GND.

In this manner, in accordance with the present embodiment, the voltagesprovided by one strong charge pump 11 are used to generate plural typesof voltages that are required for the respective operations of thememories.

Also, in accordance with the present embodiment, as described above, thestrong charge pump 11 generates a voltage of 5.0V at the time ofreading, and a voltage of 8.0V at the time of programming. The voltageto be applied to the transistor Q8 at the time of programming is 8.0V.In contrast, the operation voltage required for the main control gatelines MCG0-MCG3 at the time of reading is 4.5V.

In other words, in accordance with the present embodiment, the margin ofoutput voltage of the strong charge pump 11 is made large at the time ofreading. By this, at the time of reading, even when the voltage to beapplied to each of the main control gate lines MCG0-MCG3 changes inshort cycles, the output of the strong charge pump 11 can always bemaintained at the required operation voltage of 4.5V or greater.

Also, since the output voltage of the strong charge pump 11 has amargin, the capacity of the pool capacitor 27 can be made relativelysmall. By this, the area occupied by the pool capacitor 27 can bereduced, and thus the overall size of the apparatus can be reduced.

Also, the constant voltage circuit 17 among the constant voltagecircuits 17 and 18 that generate the voltage VPCGH operates even in thestandby mode. The constant voltage circuit 17 generates a voltage of2.5V, such that, even when the operation mode shifts from the standbymode to an active mode, such as the read mode, a memory element can beaccessed immediately after such a mode shift, moreover, the currentconsumed by the constant voltage circuit 17 is extremely small, andtherefore the current consumption at the time of standby mode can besubstantially reduced.

For example, 1.8V is used as the power supply voltage Vdd for the entireapparatus of FIG. 1. This power supply voltage Vdd can always besupplied to each sections of the apparatus.

Next, operations of the embodiment thus structured are described.

The control logic 53 of FIG. 1 outputs predetermined control signals tothe voltage generation circuit 55 according to control inputs. Accordingto the control signals, the voltage generation circuit 55 controls thestrong charge pump 11, and the constant voltage circuits 13-18.

(Operations at Read)

It can be assumed that the read mode is designated by the control logic53. In this case, the strong charge pump 11 controls the level sensor 33to generate a voltage of 5.0V. This voltage is supplied to the constantvoltage circuits 13 through 18.

The constant voltage circuit 14 adjusts the variable resistance VR1 togenerate a voltage VPYS of 4.5V at the time of reading. This voltageVPYS is supplied to the BL_select driver 21 and the Y_select driver 22.The voltage VPYS is supplied to the local bit line drivers (BSDRV0,BSDRV1) in FIG. 6.

The BL_select driver 21 (local bit line drivers (BSDRV0, BSDRV1))selects a voltage of 4.5V and outputs the same to the transistor Q8 (bitline selection transistors 217A, 217B). As a result, the bit linesBL0-BL3 can be made active.

Also, the voltage generation circuit 55 provides the voltage VPYS to theY_select driver 22, and the Y_select driver 22 selects a voltage of 4.5and applies the same to the transistor Q9. By this, the transistor Q9 isturned on, and a specified one of the bit lines BL0-BL3 is conductivelyconnected to the sense amplifier.

At the time of reading, the BL driver is not used. Also, the voltageVPBL from the constant voltage circuit 13 is not used. In this case, abit line connected to the opposing memory element is connected to thesense amplifier, and a voltage of 0V is supplied to the other three bitlines among the bit lines BL0-BL3. By so doing, data can be read out bycurrents that flow on the bit lines to which the selected memory elementand the opposing memory element are connected.

The constant voltage circuits 15 and 16 generate a voltage VPCGL of1.5V, and supplies the same to the CG decoder/driver 25. In other words,the voltage generation circuit 55 supplies the generated voltage VPCGLto the local control gate line drivers (CGDRV0-CGDRV3). The CGdecoder/driver 25 (local control gate line drivers (CGDRV0-CGDRV3))provides the voltage VPCGH of 1.5V to the main control gate line MCGthat is connected to the selected memory element.

The constant voltage circuits 17 and 18 output a voltage VPCGH of 3.0Vto the CG decoder/driver 25. The CG decoder/driver 25 (local controlgate line drivers (CGDRV0-CGDRV3)) provides the voltage VPCGH of 3.0V tothe main control gate line MCG that is connected to the opposing memoryelement.

Potential changes on each of the main control gate lines MCG at the timeof reading take place extremely fast. For this reason, a next readingmay occur before the output voltage of the strong charge pump 11recovers to the original voltage level. Even in this case, in accordancewith the present embodiment, since the output voltage of the strongcharge pump 11 is a voltage with sufficient margin (5.0V), which isgreater than the voltage required at the time of reading (3.0V), thevoltage that is provided by the constant voltage circuit 18 would notbecome lower than 3.0V.

(Operations at Programming)

Next, operations that take place when the program mode is set aredescribed.

In this case, the strong charge pump 11 controls the level sensor 33 togenerate the power supply voltage of 8.0V. The constant voltage circuit14 generates a voltage VPYS of 8.0V and supplies the same to theBL_select driver 21. The BL_select driver 21 (local bit line drivers(BSDRV0, BSDRV1)) selects a voltage of 8V and outputs the same to thetransistor Q8 (bit line selection transistors 217A, 217B). As a result,the bit lines BL0-BL3 become active.

Also, the constant voltage circuit 14 also outputs the voltage VPYS of8.0V to the Y_select driver 22. The Y_select driver 22 selects a voltageof 8.0V and applies the same to the gate of the transistor Q9. As aresult, the transistor Q9 is turned on, and a specified one of the bitlines among the bit lines BL0-BL3 can be made active.

The constant voltage circuit 13 generates a voltage VPBL of 5.2V andoutputs the same to the BL driver 23. The BL driver 23 selects a voltageof 5.2V and supplies the same to each of the bit lines BL0-BL3. Theconstant voltage circuit 16 generates a voltage VPCGL of 2.5V andsupplies the same to the CG decoder/driver 25. The CG decoder/driver 25(local control gate line drivers (CGDRV0-CGDRV3)) provides the voltageVPCGL of 2.5V to the main control gate line MCG that is connected to theopposing memory element.

The constant voltage circuit 18 generates a voltage VPCGH of 5.5V fromthe power supply voltage of 8.0V and outputs the same to the CGdecoder/driver 25. The CG decoder/driver 25 (local control gate linedrivers (CGDRV0-CGDRV3)) provides the voltage VPCGH of 5.5V to the maincontrol gate line MCG that is connected to the selected memory element.

(Operations at Erase)

Next, operations that take place when the erase mode is set aredescribed.

In this case also, the strong charge pump 11 controls the level sensor33 to generate the power supply voltage of 8.0V. The constant voltagecircuit 14 generates a voltage VPYS of 8.0V and supplies the same to theBL_select driver 21. The BL_select driver 21 (local bit line drivers(BSDRV0, BSDRV1)) selects a voltage of 8V and outputs the same to thetransistor Q8 (bit line selection transistors 217A, 217B). As a result,the bit lines BL0-BL3 become active.

Also, the constant voltage circuit 14 also outputs the voltage VPYS of8.0V to the Y_select driver 22. The Y_select driver 22 selects a voltageof 8.0V and applies the same to the gate of the transistor Q9. As aresult, the transistor Q9 is turned on, and a specified one of the bitlines among the bit lines BL0-BL3 can be made active.

The constant voltage circuit 13 generates a voltage VPBL of 5.2V andoutputs the same to the BL driver 23. The BL driver 23 selects a voltageof 5.2V and supplies the same to each of the bit lines BL0-BL3.

The negative charge pump 26 generates a voltage VNCG of −3V and suppliesthe same to the CG decoder/driver 25. The CG decoder/driver 25 (localcontrol gate line drivers (CGDRV0-CGDRV3)) provides the voltage VNCG of−3V to each of the main control gate lines MCG.

Similar operations are performed in other modes. Depending on the modes,the respective constant voltage circuits 13 through 18 create voltagesVPBL, VPYS, VPCGL and VPCGH required for read, program and eraseoperations for each of the memory elements within the memory cell arrayregion 200.

Also, in accordance with the present embodiment, in the standby mode,only the constant voltage circuit 17, one of the constant voltagecircuits 17 and 18, operates. The constant voltage circuit 17 generatesa voltage VPCGH of 2.5V, such that, even when the operation mode shiftsfrom the standby mode to an active mode such as the read mode, a highspeed access can be made immediately after such a mode shift. Also, thecurrent consumed by the constant voltage circuit 17 in the standby modeis extremely small, and therefore the current consumption at the time ofstandby mode can be substantially reduced.

The word gate voltage generation circuit 20 generates a voltage VPWLthat is supplied to each of the word lines WL0, WL1, . . . The voltageVPWL is supplied to the local word line drivers (WLDRV0-WLDRV63). As aresult, the local word line drivers (WLDRV0-WLDRV63) apply predeterminedvoltages to the respective word lines WL0, WL1, . . .

In this manner, in accordance with the present embodiment, one chargepump circuit and a plurality of regulators are used to acquire aplurality of operating voltages required for each of the operationmodes. As a result, the area occupied by the circuits can be reduced andthe cost can be lowered, and the current consumption can be restricted.

Also, in accordance with the present embodiment, the margin of outputvoltage of the strong charge pump 11 is made large at the time ofreading. By this, at the time of reading, even when the voltage to beapplied to each of the main control gate lines MCG0-MCG3 changes inshort cycles, the output of the strong charge pump 11 can always bemaintained at the required operation voltage or greater. Also, since theoutput voltage of the strong charge pump 11 has a margin, the capacityof the pool capacitor 27 can be made relatively small. By this, the areaoccupied by the pool capacitor 27 can be reduced, and thus the overallsize of the apparatus can be reduced.

Also, in accordance with the present embodiment, at the time of standbymode, only the constant voltage circuit 17 with a low currentconsumption is operated, and the constant voltage circuit 18 for activemodes is not operated. As a result, the current consumption in thestandby mode can be substantially reduced.

The present invention is not limited to the embodiments described above,and many medications can be made and implemented within the scope of thesubject matter of the present invention.

For example, the structure of the non-volatile memory element 108A, 108Bis not limited to the MONOS structure. The present invention can beapplied to a non-volatile semiconductor memory apparatus that uses twinmemory cells of a variety of other types, which can trap charge at twolocations independently from one another, by using one word gate 104,and the first and second control gates 106A and 106B.

Also, in the embodiment described above, the division number of sectors,the division number of large blocks and small blocks, and the number ofmemory cells in each small block are presented as examples, and variousother modifications can be made. The division number of large blocksthat is 8 was determined in view of the restrictions derived from themetal wiring pitches. If the metal wiring pitches can be narrowed, thedivision number can be further increased. For example, with 16 dividedblocks, the load capacity (gate capacity) of each one of the controlgate lines is further reduced, such that a higher speed driving becomespossible. However, with the 16 divided blocks, as the number of maincontrol gate lines increases, the lines and spaces must be narrowed, orthe area must be increased. Also, the number of control gate driversincreases, which results in a greater area.

[Effects Of The Invention]

With the present invention described above, the following effects can beachieved. As a regulator for standby with a low current consumption isused, the power consumption at the time of standby can be significantlyreduced.

What is claimed is:
 1. A non-volatile semiconductor memory apparatus,comprising: a charge pump device that steps up and outputs a powersupply voltage; a memory array formed of a plurality of non-volatilememory elements; an operation voltage setting device that sets operationvoltages to execute plural modes for a specified non-volatile memoryelement of the plurality of non-volatile memory elements; a constantvoltage device for activation that is provided with voltages output fromthe charge pump device to generate the operation voltages in an activestate; and a constant voltage device for standby that is provided with avoltage output from the charge pump device to generate a voltage basedon the operation voltage with a lower current consumption than voltagesgenerated by the constant voltage device for activation.
 2. Thenon-volatile semiconductor memory apparatus according to claim 1, theoperation voltage generated by the constant voltage device for standbybeing a voltage higher than the power supply voltage.
 3. Thenon-volatile semiconductor memory apparatus according to claim 1, theconstant voltage device for standby generating an operation voltage fora read mode for the non-volatile memory element.
 4. The non-volatilesemiconductor memory apparatus according to claim 1, the charge pumpdevice stepping up the power supply voltage to generate a plurality ofvoltages.
 5. The non-volatile semiconductor memory apparatus accordingto claim 1, the constant voltage device being capable of generatingconstant voltages of different voltage values depending on read, programor erase mode for the non-volatile memory element.
 6. The non-volatilesemiconductor memory apparatus according to claim 1, the non-volatilememory element being a memory element that forms a twin memory cellcontrolled by one word gate and first and second control gates.
 7. Thenon-volatile semiconductor memory apparatus according to claim 6, theoperation voltage setting device setting voltage values provided fromthe constant voltage devices independently for the first and secondcontrol gates, and an impurity layer to access trapped charge of thenon-volatile memory element.
 8. The non-volatile semiconductor memoryapparatus according to claim 6, the operation voltage setting deviceincluding: a word line connected to a word gate of the twin memory cellin the same row; a control gate line that is commonly connected to themutually adjacent first and second control gates in the same column ofthe twin memory cells arranged adjacent to each other in a rowdirection; and a bit line that is commonly connected to impurity layersto access trapped charge arranged in the same column of the mutuallyadjacent non-volatile memory elements of the twin memory cells arrangedadjacent to each other in the row direction, voltage values providedfrom the constant voltage devices being set independently for thecontrol gate line and the bit line.
 9. The non-volatile semiconductormemory apparatus according to claim 1, the non-volatile memory elementincluding an ONO film formed of an oxide film (O), a nitride film (N)and an oxide film (O) as a charge trap site.
 10. A non-volatilesemiconductor memory apparatus, comprising: a charge pump device thatsteps up and outputs a power supply voltage; a memory array formed of aplurality of twin memory cells that each have two non-volatile memoryelements; an operation voltage setting device that sets an operationvoltage to execute each of reading, programming and erasing operationsfor a specified non-volatile memory element of the plurality of twinmemory cells that each have two non-volatile memory elements controlledby one word gate, and first and second control gates; a constant voltagedevice for activation that is provided with voltages output from thecharge pump device to generate the operation voltages in an active mode;and a constant voltage device for standby that is provided with avoltage output from the charge pump device to generate in an active modea voltage based on the operation voltage to be supplied to the first andsecond control gates in a read mode with a lower current consumptionthan voltages generated by the constant voltage device for activation.